Does your weight affect how well your birth control works?

The effectiveness of almost all types of birth control will not be impacted by your weight. Two exceptions are the patch and emergency contraception.

For the patch, Xulane may be less effective if you weigh more than 198 pounds. Twirla, the other patch option, may be less effective at preventing pregnancy if your BMI is 25 or greater, and it should not be used at all if your BMI is 30 or greater because of decreased effectiveness and a potentially increased risk of blood clots.

When it comes to emergency contraception, over-the counter levonorgestrel-based emergency contraception, like Plan B One-Step, Next Choice One Dose, and others, may not be as effective in people who weigh 165 pounds or more. Ella, which is prescription-only emergency contraception, is equally effective in people who weigh between 165 and 194 pounds as it is in people who weigh under 165 pounds. But ella may not work as well if you weigh 195 pounds or more. The copper IUD and IUDs with 52mg of levonorgestrel (Mirena and Liletta) are the only emergency contraception options proven equally effective if you weigh 195 pounds or more. IUDs are also the most effective form of emergency contraception for everyone, regardless of weight.